User does not respond to 'devise' method

I’ve recently went back to an old project and it seems to have stopped working giving me this error: ~/projectx/vendor/ruby/1.9.1/gems/devise-2.0.0/lib/devise/rails/routes.rb:391:in `raise_no_devise_method_error!': User does not respond to 'devise' method. This usually means you haven't loaded your ORM file or it's being loaded too late. To fix it, be sure to require 'devise/orm/YOUR_ORM' inside 'config/initializers/devise.rb' or before your application...